Belt sometimes goes off under the rain

Hello,

No rain during 4 days in France : no problem.
But today, rain was back… and the belt went off.

I analysed and I think I understand the problem.
The snubber seems not to be centered, and when it is rainy, some dirty elements from the road are sticking on the belt. Then the belt and these elements touch the snubber more firmly, and the belt goes to the space on the left.

What do you think about that ?